That's a typical interlace problem with very thin lines. It's a limitation of interlaced video. The problem is that the lines are one scan line thin and as the odd and even scan lines are displayed, they flicker on and off. Try rendering progressive 24p and they should disappear.

If want to deliver 29.97 and you have already enabled "Reduce Interlace Flicker" then you can try adding a Gaussian Blur with just 0.002 in the vertical direction. This blurs the thin lines so that they occupy more than one scan line and reduces the flickering.

Should have checked further before that last post. I tried rendering that section in 24p and it definitely cleared it up. I will try to render the whole project that way and it looks like that will solve the problem. Thanks so much for you help, John and hope you have a very Merry Christmas!